Draft-control system



W. P. CHANDLER, JR

DRAFT CONTROL SYSTEM Filed July 11, 1927 INVENTOR WITNESSES Patented 0a. 2, 1928.

UNITED STATES DRAFT-CONTROL sYsrErt.

Application filed July 11,

This invention relates to regenerative heating furnaces, and has particularly to do with mechanism for regulating their draft.

In a combustion furnace the effectiveness of a draft acting upon it through its flue is in inverse relationship withthe absolute pressure in the flue through which the prod,- ucts of combustion flow, the absolute pressure, in order to insure any draft, being necessarily under atmospheric pressure. Stated differently, when the absolute pressure in a flue diminishes, the draft on the furnace increases, and when such pressure increases the draft decreases. In a regenerative heating furnace, each of its several flues lead either directly or indirectly from the furnace through a regenerator to a stack or equivalent draft-inducing means, so that the draft acting upon the furnace through a particular flue must exert its action through the regenerator forming a part of the flue. Therefore, the effectiveness of the draft acting upon the furnace through the portion of a flue at the inlet side of a regenerator depends largely upon the draft resistance offered by theregenerator which forms part of the flue.

In the operation of regenerative heatin furnaces, the products of combustion carry with them variable amounts of dust which variably clog the checkerwork of the regenerators, and accordingly variably reduce the effective draft in the portions of the flues between the furnace and the regenerator chambers.

The object of this invention isto provide simple and effective mechanism for auto,- matically regulating the draft on regenerative heating furnaces to the end that a predeterminedv substantially uniform amount thereof may act upon the furnace regardless of through which of its regenerators the products of combustion may be passing.

According to thi invention, mechanism is provided for automatically regulating the draft inducing means of a regenerative heating furnace in inverse relationship with the absolute pressure in the regenerative inlet side of the particular flue through which the products of combustion flow. Depending upon the type of regenerative furnace to which the invention is applied, that is to say, whether it be to a reversing furnace or to a furnace in which the products for and of combustion flow continuously in one direction, the flues may lead from the opposite 1927. Serial No. 204,682.

ends or sides of the furnace, or they may lead from but one end or side. From the regenerator inlet side of each of the flues, a flue-prcssure-communicating valve-controlled condult leads to a mechanism for controlling a draft inducing means such as a stack. WVhile various forms of control mechanism may be employed, it is preferred to use a float mechanism adapted to be actuated by the pressure in the flue-pressure conduit which is in communication with the flue through which the products of combustion are flowing, the float mechanism having a movable part mechanically or otherwise connected to a stack damper. Because of the relatively low pressures and small variations- 1n them thusutilized for regulating the stack damper,'it is preferred to use a liquid seal valve for placing the float mechanism in communication with one or the other of the conduits, and, to facilitate the operation of the furnace and its draft control mechanism, the operation of such valve is preferably coordinated with the furnace reversing or equivalent mechanism.

In the accompanying drawing the invention is diagrammatically illustrated in its applicability to a regenerative reversing open hearth steel furnace, the drawing showing a vertical longitudinal sectional view of the furnace and its regenerators.

In the drawing a furnace 1 is shown hav,- mg at its ends fuel inlets 3 and 4, and like- I Wise flues 5 and 6, leading respectively to and through regenerators 7 and 8, and passto a common duct 9, which leads to a stack 10 provided with a damper 11. The flow of products of combustion through the flues and regenerators, is reversed by two alternately acting dampers 13 and 14, which effectively prevent the draft from acting on more than one flue at a time, and which are connected by cables 15 and 16 to a lever or beam 17 fulcrumed at 18, and carrying an operatingarm 19. The movements ofthe beam close one flue and open the other.

Air necessary for combustion is supplied through air valves 20 and 21 to the flue which is not operating to remove, waste gases. These ports are controlled by the mechanism used to operate the dampers 13 and 14, so

- ing fronrthe outlet sides of the regenerators that as the flow of waste gas through the flues is reversed, the air flow is also automatically reversed. This is accomplished by cables 22 and 23 to drums 24 and 25, which are operated by two other concentric drums 26' and 2'4. Cables 28 and 29 connected to lever 17 pass around the drums 26 and 27, and end in counter-weights 30 and 31.

Pipes 32 and 33, connected to the regenerator inlet side of fines 5 and 6, communicate the due pressure to a liquid seal valve comprising a. casing 34, covered by a lid 35, from which depend two pressure tight partitions 36 and 37, and a partition 38 extends upwardly from the base intermediate them. A suitable liquid 39, placed within the casing, is displaced alternately in either main chamber by one of a pair of fluid displacers 40 and 41 attached by cables 42 and 43 to a beam 44, fulcrumed at 45, and carrying an operating arm 46 which is connected by a link 47 to the operating arm 19 of lever 17.

As arm 19 is thrown from one position to another, arm 46 simultaneously moves with it, thus reversing the position of dampers 13 and 14 and valves 20 and 21, as well as of displacers 40 and 41, the result being that the liquid in one chamber rises and thereby closes off the conduit connected to the flue which carries air to the furnace, and at the same time unseals the other conduit, con- 'nected to the flue which now carries the products of combustion from the furnace to the stack.

The flue pressure from the unsealed pipe is conducted from valve casing 34 by a pipe 48 to regulating mechanism 49 comprising a casing 50 containing a liquid 51, and having suspended in it a pair of bells 52 and 53 carried by a beam 54 pivotally supported on a fulcrum Beam 54 carries on its upper side an operating arm 56, attached to which is a cable 57 passing over sheaves 58, and fastened at its other end to a drum 59. Mounted on the same shaft is another drum. 60 carrying the draft damper 11, and around this drum passes a cable 61 which extends over sheave 62 and has its free end attached to a counter-weight 63. Referring again to the. float mechanism, it will be seen that pipe 48 ends under bell 54. A pipe 64 open to the atmosphere is inserted under the other bell to re-lieve any suction or pressure under the bell, and a weight 65 is placed thereon for the purpose hereinafter described.

With the parts in the positions illustrated in the drawing, the operation is as follows: Flue 6 being closed by damper 14, draft is exerted upon flue 5. Air entering fine 6 from port 21 flows in the direction shown by the arrows to the furnace where it meets the fuel. The products of combustion pass out of the furance through fine 5. flow through regenerator 7 and pass to the atmosphere through duct 9 and stack 10. When the dampers 13 and 14 are set in the positions 'shown, 'displacer 41 is automatically depressed to cause the liquid to. rise and seal iceeaaea conduit 33, and float 40 is raised to cause the liquid on that side to fall and unseal conduit 32. This permits the pressure in the regenerator inlet side of flue 5 to be communicated through conduit 48 to the bell 52 in the regulator. lVith normal draft, the absolute pressure under bell 52 is below atmospheric, and the weight 65 is used as a counterbalance, it being of such size and in such position that, when a predetermined pressure-draft relationship is present, the beam 54 will be in equilibrium.

If the regenerator inlet pressure in flue 5 increases, beam 54 moves in clockwise direction to open damper 11 until the proper draft condition with respect to the pressure in conduit 32 is re-established @n the other hand, if the pressure at the regenerator inlet decreases, lever 54 moves counterclockwise and the damper is automatically J closed up to the point where the correct relationship is reestablished.

To reverse the operation of the furnace, the right hand end of beam 1? is thrown upwardly, thereby closing damper 13 and valve 21, and opening damper 14 and valve 20. At the same time, operating arm 19 acts through link 47 to move beam 44, lowering displace-r 40, which causes the liquid to rise and seal pipe 32, and at the same time displacer 41 rises and unseals pipe 33. The passage of air and the products of combustion are then in a direction opposite to that shown by the arrows in the r drawing, and the pressure in flue 6 is efiective to operate regulator 49, which latter operates in the same. manner as previously described to control the draft induced in flue 6 by stack 11 in accordance with the pressure in the regenerator inlet side of that flue.

In the specification and appended claims the term operative flue has for convenience been used to designate that flue which carries the products of combustion from the furnace.

According to the provisions of the patent statutes, l have explained the principle and operation of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scopeof the appended claims, the invention may be practiced by other forms of construction than that particularly illustrated and described.

I claim 1. The combination with a regenerative for inducing draft through the furnace and flues, and mechanism for automatically regulating said draft-inducing means to vary its effectiveness in inverse relationship with the pressure in the regenerator inlet side of each flue when products of combustion flow through the flue.

2. The combination with a regenerative heating furnace, a plurality of regenerator-s, flues leading from said furnace and extending one through each of said regenerators,

and means for rendering in alternation'each of said flues effective for the flow of products of combustion from the furnace through one of the regenerators; of a draft-inducing stack connected to said flues at their regenerator outlet sides, a damper in said stack, and mechanism for automatically regulatin the position of said damper to vary the d raft-inducing effectiveness of said stack in inverse relationship with the pressure in the regenerator inlet side of each flue when products of combustion flow through the flue.

3. The combination with a regenerative heating furnace, a pair of regenerators, a pair of flues leading from said furnace and extending one through each of said regenerators, and means for rendering in alternation each of said flues effective for the flow of products of combustion from the furnace through one of the regcnerators; of means acting on said flues at the outlet sides of the regenerators for inducing draft through the furnace and flues, and mechanism for automatically regulating said draft-inducing means to vary its effectiveness in inverse relationship wlth the pressure in the regenerator inlet side of each flue when products of combustion flow through the-flue.

4. The combination with a regenerative heating furnace, a pair of regenerators, a pair of flues leading from said furnace and extending one through each of said regenerators, and means for rendering in alternation each of said flues effective for the flow of products of combustion from the furnace through one of the regenerators; of a draftinducing stack connected to said flues at their regenerator outlet sides, a damper in said stack, and mechanism for automatically regulating the osition of said damper to vary the draft-in ucing effectiveness of said stack; in inverse relationship with the pressure on the regenerator inlet side of each-flue when products of combustion flow through the flue, i

-5. The combination with a regenerative heating furnace, a plurality of regenerators, flues leading from said furnace and extending one through each of said regenerators, and means for rendering in alternation each of said flues effective for the flow of products of combustion from the furnace through one of the regenerators; of means acting on said flues at the outlet sides of the regeneratorr for inducing draft through the furnace and flues, and float-actuated mechanism for regulating automatically said draft-inducing means to vary its effectiveness in inverse relationship with the pressure in the regenerator inlet side of each flue when products of combustion flow through the flue.

6. The combination with a regenerative heating furnace, a-pair of regenerators, a pair of flues leading from said furnace and extending one through each of said regenerators, and means for rendering in alternation each of said flues effective for the flow of products of combustion from the furnace through one of the regenerators; of a draft inducing stack connected to said flues at their regenerator outlet sides, a damper in said stack, and float-actuated mechanism for automatically regulating the position of said damper to vary the draftinducing effectiveness of said stack in inverse relationship with the pressure on the regenerator'inlet side of each flue when prod ucts of combustion flow through the flue.

7. The combination with a regenerative heating furnace, a plurality of regenerators, flues leading from said furnace and extending one through each of said regenerators, and means for rendering in alternation each of said flues effective for the flow of prodnets of combustion from the furnace through one of the regenerators; of means acting on said flues at the outlet sides of the regenerators for inducing draft through the furnace and flues, pressure communicating conduits extending one from the regenerator inlet side of each of said flues, and pressure actuated mechanism connected to said conduits for automatically regulating said draft-inducing means to vary its effectiveness in inverse relationship with the pressure "in the regenerator inlet side of each flue when products of combustion flow through the flue. Y

8. The combination with a regenerative heating furnace, a pair of regenerators, a pair of flues leading from said furnace and extending one through each of said regenerators, and means for rendering in alternation each of said flues effective for the flow of products of combustion from the furnace through one of the regenerators; of a draft-inducing stack connected to said flues attheir regenerator outlet sides, a damper in said stack, a pair of conduits extending one from the regenerator inlet side of each.

of said flues, and pressure actuated mecha- 'nism connected to said conduits for automatically regulating the position of said damper to vary the draft-inducing effectiveness of said stack in inverse relationship with the pressure on the regenerator inlet side of each flue when products of combustion flow through the flue.

;= 7 reeeaea 9. The combination With a regenerative heating furnace, a pair of regenerators, Hues leading one from each end of said furnace and extending one through each of said'regenerators; reversing mechanism for render- "ing said flue alternately eflective for the flow of products of combustion from the furnace through one of the regenerators; of a draft-inducing stack connected to said fines at their regenerator outlet sides, a damper in said stack, float-actuated mechanism for regulating said damper, pressure-communicating conduits extending one from the regenerator inlet side of each of said fines, a

third conduit communicating with said float mechanism, a liquid seat valve for centroiling communication between one or the other of said first-named conduits and said third conduit, and means coordinated with. said reversing mechanism for operating said valve whereby the pressure in the regenerator inlet side of each flue is when products of combustion flow through the fine rendered effective to actuate said float mechanism to in turn regulate said. damper to vary the draft inducing effectiveness of said stack. In testimony whereof, I sign my name.

"WILLARD P. CHANDLER, JR. 

